Two studies published this year yield conflicting results on whether fortifying flour with essential vitamins and minerals improves anemia prevalence. One study published in the British Journal of Nutrition (BJN) showed that each year of flour fortification was associated with a 2.4% decrease in anemia prevalence among non-pregnant women. The second study published in Nutrition Reviews provided little evidence that fortification improved anemia prevalence.
So does fortification affect anemia or not? As an author on both studies, I suggest that the answer depends entirely on the quality of the fortification program.
This is an important question because an estimated 243 million non-pregnant women of child-bearing age, 16 million pregnant women, and 114 million children worldwide suffer from anemia related to iron deficiency, according to the World Health Organization (WHO) Global Prevalence of Anemia in 2011 report. Women who have had iron deficiency anemia say it causes debilitating fatigue. In pregnancy, anemia contributes to 20% of all maternal deaths. In childhood, anemia limits cognitive development.
Currently 83 countries require wheat flour fortification as part of the industrial milling process. Fourteen of these countries also mandate wheat flour fortification. Iron is the most frequently added nutrient, and flour is also commonly fortified with the B vitamins folic acid, riboflavin, and B12. Deficiencies in each of these nutrients can cause anemia. Knowing how effective these fortification programs are is a critical step in recommending ways to improve them.
For the BJN study, we looked at countries that included at least iron, folic acid, vitamin A or vitamin B12 in their fortification programs. Their fortification programs could include wheat flour alone or combined with maize flour. The papers included in this study all included anemia prevalence in non-pregnant women as reported in national surveys, such as the Demographic Health Surveys and Multiple Indicator Cluster Surveys. Countries were included if they had anemia data from before and after fortification began. Twelve countries that we called “fortification countries” met this criteria. We found 20 countries with at least two national surveys on anemia but no flour fortification program.
Since anemia is affected by many things, we adjusted the findings for the Human Development Index and malaria. In the 12 fortification countries, each year of fortification was associated with a 2.4% decline in anemia prevalence. In comparison, the non-fortification countries had a 0.1% decline in anemia prevalence over time.
The study published in Nutrition Reviews was a systematic review of programs to fortify flour. Only programs to fortify flour with iron were included. We found published and unpublished reports of fortification programs in 13 countries. Each report compared data collected before fortification with data collected at least 12 months after fortification. That review showed that fortification consistently improved women’s iron status, but it provided little evidence that fortification improved anemia prevalence.
This was perplexing. How could two studies conducted practically simultaneously on the same topic produce such different results?
One difference was that all data in the BJN report were from national studies while the Nutrition Reviews paper included both national and sub-national data . Most studies presented data gathered at the subnational level within a selected area of the country; the only national-level data reported were for Fiji and Uzbekistan. The major difference, however, was noted by Richard Hurrell, Professor Emeritus for Human Nutrition, ETH Zurich. He was not involved in writing either paper, but he made an important observation in a letter to the editor of the British Journal of Nutrition. Most of the 12 fortification countries in the BJN study had national programs that used iron compounds recommended by the World Health Organization (WHO).
In contrast, most of the studies in the systematic review did not use the WHO-recommended iron compound and did not add the minimum recommended iron level. Most of these reports showed no decline in anemia prevalence with flour fortification. In addition, the programs in the Nutrition Reviews paper reflected a wide variety of compliance with the fortification standard and the percent of population covered by fortified products.
Fortification programs cannot be expected to have a significant health impact if the iron compounds are not bioavailable , meaning if they are not easily absorbed by the human body. Also, programs will not have the expected impact if insufficient iron amounts are used, if the program is not well-monitored, or if a high proportion of the population does not consume fortified foods.
On the other hand, well-planned, fully implemented and carefully monitored programs to fortify flour with the recommended level of essential vitamins and minerals will reduce the risk of anemia from nutritional deficiencies over time.
Featured image: “Flour” by Melissa Wiese, CC BY 2.0 via Flickr.